Poor Man's CNC Edge Finder




Introduction: Poor Man's CNC Edge Finder

Aluminum foil tape offers a very simple, precise and cheap way to zero almost any workpiece.

Things you need:

  • Aluminum foil tape - it can be found at most hardware stores.
  • One or two alligator clips.
  • A 100nF ceramic capacitor (optional but recommended)
  • A CNC controller with sensor assisted edge finding capabilities like Estlcam

Step 1: How It Works

How it works:

  • The aluminum tape and tool act as switch. Once the tool touches the tape the circuit is completed and the probe input of the CNC controller triggers.
  • The aluminum tape is connected to the probe input using an alligator clip.
    (Pin D6 for Estlcam / A5 for GRBL)
  • The tool is connected to GND
    • I've connected GND to the spindle housing as it is conductive all the way through to the tool.
      (Check this first - not all spindle housings are conductive and connected to the tool.)
    • This way the GND connection can stay permanently and you can even touch off with the spindle running.
  • Add a 100nF ceramic capacitor between probe input and GND close to the controller - this suppresses interferences which may trigger the input unintentionally.

Step 2: Prepare the Tape

Prepare the tape:

  • Prefer tape with liner - it is easier to work with.
  • Cut a short length of tape from the roll and turn it over.
  • Fold the liner back lengthwise to expose the upper half of the glued aluminum foil.
  • Then fold about 5mm (1/4") of the tape itself down and put the liner back.
  • Finally cut the tape into short stripes.


  • Ready to use strips.
  • Liner can be removed easily.
  • Folded back part of the tape does not keep sticking to the alligator clip.

Step 3: Final Thoughts

You'll find most information in the video at the beginning - so just a few final thoughts:

  • The tape can be reused several times. The wrinkles add some thickness and therefore error but for most applications this should be insignificant (I've measured a difference of 0.02mm / 0.0008" between new and badly wrinkled tape)
  • This also works for conductive workpieces with a small modification, even if the machine bed and workpiece is connected to GND. Just put regular tape below the aluminum tape to add an isolation layer.
  • Be careful with coated tools. Some coatings are non-conductive so the circuit will not close -> risk of breaking the tool. If in doubt check the tool with a multimeter first.
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    Question 2 years ago on Step 1


    I just bought a CNC 3018 Pro and I would like to know if your edge finder method, with Estlcam, can works with it. Is it compatible? If yes, what is the pin out to connect alligator able?

    Thank you


    Bob Wright17
    Bob Wright17

    Question 3 years ago on Step 3

    Hi Can this work with Mach3
    Is there a Script for this


    6 years ago

    The aluminum tape idea is brilliant. Well-done!


    6 years ago

    The tape is lets say 0.004 your bit is 0.500 your dead center is 0.252 When using vertical tape 0.004, subtract 0.004 for vertical end


    6 years ago

    Cool technique